Question

Given below are two statements:
Statement I: Haemoglobin and methaemoglobin are intracellular electron carriers in RedOx reactions to drive ATP synthesis.
Statement II: Isoprenoids( Ubiquinone, CoQ, Plastoquinone) are lipophilic electron carriers in RedOx reaction to drive ATP synthesis.
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Lipophilic Electron Carriers: Coenzyme Q (Ubiquinone, 10 isoprene units) and Plastoquinone shuttle electrons in respiratory and photosynthetic membranes. Hemoglobin is an oxygen transporter.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Respiratory and photosynthetic electron transport chains utilize mobile lipid-soluble isoprenoid quinones to shuttle electrons between multiprotein complexes.

Step 2: Detailed Explanation:
1. Statement I: Hemoglobin is a specialized respiratory metalloprotein designed for reversible oxygen transport in erythrocytes, and Methemoglobin is an oxidized, non-functional pathological derivative. Neither functions as an electron transport carrier to drive ATP synthesis in mitochondria. Hence, Statement I is false.
2. Statement II: Ubiquinone (Coenzyme Q CoQ) in the mitochondrial inner membrane and Plastoquinone in chloroplast thylakoid membranes are small, mobile, lipophilic benzoquinones with long polyisoprenoid tails that undergo reversible two-electron/two-proton redox reactions ($Q \leftrightarrow QH_2$) to drive proton-motive force generation and ATP synthesis. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Statement I is false but Statement II is true, matching option (D).